1. Field of the Invention
This invention relates to an improvement to a film carrier tape to be used for tape automated bonding (TAB).
2. Description of the Related Art
A semiconductor device which is finished by tape automated bonding (hereinafter referred to TAB) is normally subjected to two probing tests, which are conducted before and after mounting an IC chip on a film carrier tape.
The first probing test is carried out electrically by bringing the bumps 12 of an IC chip 11 into contact with respective probes 14 of a stationary card 13 of a testing instrument as illustrated in FIG. 1 of the accompanying drawings, while the second probing test is also an electric test where testing areas 17 of the conductive leads 16 of a film carrier tape 15 are brought into contact with respective probes 14 of a stationary card 13 of a testing instrument.
When a semiconductor device passed the above described tests, the film carrier tape 15 carrying the device is cut along a number of cutting marks 20 shown in FIG. 3A to separate the device from the tape and produce an independent product 21 as shown in FIG. 3B. Then, the exposed front end portions 22 of leads extending from an insulation layer 18 are bonded to the substrate to bring forth a completely finished semiconductor device.
There may be cases, however, where a finished semiconductor device 21 that has passed two probing tests as described above needs to be tested for another time. Now, the leads 16 of the device are mostly covered by the insulation layer 18 which is made of a resist to protect the device and only slightly exposed out of the insulation layer 18 at the front ends. Obviously, it is a very difficult job to make the tiny front end portions of the leads contact with probes of a stationary card of a testing instrument.
Moreover, if a semiconductor device whose leads have been bonded to the substrate needs to be tested, they must be separated from the substrate in the first instance at the risk of damaging them to bring the device out of order once and for all.
Besides, when a final product 21 is tested by bringing the front end portions of the leads into contact with respective probes of a testing instrument and it is found to be faulty, there is no way to determine if the fault is in the IC chip or somewhere in the leads.
In an attempt to overcome this drawback, there has been proposed a method of separating the IC chip main body from the film carrier tape that carries the chip by means of some chemical agent so that it may be subjected to a test with ease. But, again, such a method is not without danger of damaging the IC chip and exfoliating the bumps on the chip. Therefore, such a chemical method is practically not feasible.
Under these circumstances, a semiconductor device can only be visually checked if it is found faulty after installing the IC chip on the substrate and, therefore, there is no way to pinpoint the trouble of the device to find out if the fault is in the IC chip or somewhere in the leads.